Greetings all,


It has been a long time since I've been on the forum. Hope you're all doing fine. Technically speaking, not being on here means no issues.... and yeah, surprisingly 'her majesty' has been very reliable lately. That only lasts so long of course ;-) So here we are - yet another coolant leak (or it so appears). I have fixed 3 in the past already, and the issues have all been relatively easy to spot / fix. This time... can't find. I have inspected the engine a few times already, engine running and hot, manually revving time to time, and see nor smell anything that would relate to an obvious coolant leak. Only element I can tell is that I have found relatively small 'puddle' of coolant on the ground after it has been parked for a while, engine off. What I noticed more recently is a relatively 'moist' surrounding around the (top) expansion tank. Around the cap that is. It was dry the last time I looked at it. Cap is closed tight. So question is - can it leak from there? Are these caps known to become defect? I think this cap has its importance / role is the cooling system (besides closing the tank of course) in the coolant distribution between engine and secondary expansion tank. A new cap is cheap - so considering replacing anyway, but wondering if I'm onto something or not possible to be the source of my problem. I do have my eye on one of the two non-return valves in the hose matrix. I already have replaced a cracked one (the source of an earlier leak). This other one doesn't appear cracked, but also had some moist building up recently that looked unusual. Thoughts?


Cheers

 

The coolant reservoir is a failure point for several reasons. The plastic will crack and drip on the left side cat and vaporize without leaving any moisture. The tank can crack so that coolant escapes as a fine mist leaving no trace. The float can get stuck on its tube and give false 'low coolant' alarms. The cap 'O' ring can loose seal and create strange coolant movement issues.

A pressure test with a 'rented' test kit can identify issues with the tank but not the cap.

In short, the tank is a source of a number of issues and can be easily replaced for under $100.

New Jaguar XK8 Expansion Tank Coolant Bottle Reservoir 1997 2006 MJD4400AB | eBay

 

Many thanks Test Point. I like this option. Even if ends up not being the real source of my problem, it's not a bad idea to replace at this point of time and an easy 'peace of mind' for ~$100


Cheers